9401.91 - Of wood:

This HTS category, 9401.91, specifically pertains to parts of seats that are constructed from wood. This includes components for various types of seating such as chairs, stools, benches, and sofas, provided that the primary material of these parts is wood. The scope covers any wooden component designed for use in the assembly, repair, or completion of such seating articles, excluding complete seats themselves.

This category is distinguished from its sibling, 9401.99, which covers parts of seats made from materials other than wood, such as metal, plastic, or fabric. Therefore, the defining characteristic for classification under 9401.91 is the material composition of the seat part itself, specifically its wooden construction.

Within this category, further subdivisions exist to provide more granular classification. Subcategory 9401.91.15.00 addresses parts made of wood for seats specifically designed for use in motor vehicles, distinguishing them by their intended application and potentially unique structural requirements. Category 9401.91.20.00 carves out wooden parts originating from bent wood seats, acknowledging a specific manufacturing process and aesthetic. Finally, 9401.91.90 serves as a residual category for all other wooden seat parts not otherwise specified, ensuring comprehensive coverage within the "of wood" classification.